Supervisory circuit for telephone switchboards



Dec. 26, 1939. P, BQYER, JR 2,184,268

SUPERVISORY CIRCUIT FOR TELEPHONE SWITCHBOARDS Filed Feb. 4,1959

CIR QUIT N0.

CIR CU/T N0. 2 Q CIR CL/IT N0 5 106' INVENTOR RicharJBBoyer; J11

ATTO NEY Patented Dec. 26, 1939 UNITED STATES PATENT ()FFICE Richard P. Boyer, Jr.. Newton, Mass. Application February 4, 1939, Serial No. 254,693

' 9 Claims. (01. 179-51) This invention relates to telephone circuits and has particular reference to switchboard circuits of the cordless type.

One of the objects of my invention is to provide a switchboard so constructed that the operator in charge will be advised when any of two or more connected parties has hung up and also which circuit in the switchboard needs attention following the discontinuance of use by any subscribers who may be connected to the switchboard.

A further object of my invention is to provide visual signalling means of a type that is very effective in calling the operators attention to the circuits when changes need to be made.

Another object of my invention is to provide means for indicating to the operator when a party called by the operator has answered.

These and other objects of my invention will become apparent as the description proceeds with m the aid of the accompanying drawing in which Fig. 1 is a diagram of two connected lines in conjunction with my supervisory circuit as applied to one switchboard circuit.

Fig. 2 is a diagram of my supervisory circuit 25 showing how it may be applied to one switchboard circuit and any number of lines.

Fig. 3 is a diagrammatic view of a typical type of cordless switchboard utilizing my circuit.

Referring to Fig. 1, the diagram shown in light 3 lines represents a pair of lines extending to the Y switchboard and a connecting circuit in the switchboard. In practice, of course, there are a plurality of lines extending to the switchboard, and, in the switchboard, there will be a plurality of connecting circuits whereby the incoming lines may be connected to each other through different circuits as desired or depending on what circuits happen to be busy at the time the additional lines are to be connected.

In the drawing one subscriber is represented at 2 and the other subscriber at l. The lines from these subscribers run to the switchboard on circuits 6 and 8. Intermediate thereof are ringing keys Ill and I2 by means of which alternating current may be impressed on circuits 5 and 8 to ring the subscribers bells when desired.

One of the wires of circuit 6 passes through the ringing key ID to wire l4, through key-operated switch Hi to wire l8, which in turn is connected to the retard coil 20, and thus to the positive terminal of battery 22.

The other wire of circuit 6 passes through the ringing key H! to the relay 24, through key-operated switch 26 to wire 28, to retard coil 30, to the negative terminal of battery 22.

A separate circuit influenced by the relay 24 runs from ground 32 to switch 34, which is opened or closed by the operation of relay 2%, to wire 36, which divides at 38, one path going to a lamp 40, which is known as a busy lamp, on through wire a 42 to junction 44, and thence to thepositive terminal of battery 22. From junct on 38 the circuit also goes through resistance 46 to wire 68, to switch 5! and thence to. junction 52 from which the circuit goes in one path to relay 53, on to the 10 ground at 56. From junction 52 extends another wire 58 which is connected to all other key switching connections corresponding to switch 50 on the same connecting circuit, as will be more particularly expla ned hereinafter. 5

From junction 44 extends a wire 66, which may, if desired-pass through a relay 52 controlling an audible signal or buzzer, and thence through wire 64 to lamp 66, which lamp is known as a supervisory signal, and to which lamp is connected the switch 68 controlled by the operation of relay 54.

The switches "5,26 and 50 are all under the control of a single key. For example, such a key may be key 10 in Fig. 3, which when thrown upwarolly will close the three switches H5, 28 and 58 in circuit No. 1 of the switchboard. This, of course, assumes that circuit 6 coming from subscriber 2 is under the control of the switches in the column indicated by the arrow F2 in Fig. 3. 30

The procedure in signalling the operator is as 1 follows. A subscriber removes his receiver from the hook, thereby closing a circuit to the line lamps 13 indicated in Fig. 3. The line lamp circuit, being conventional, is not shown. The operator, observing the lighted linelamp of the particular subscribers line, thereupon moves a switchboard key associated with that lineto connect the line with any connecting circuit on the board not in use. For example, key it may be moved forwardly to connect subscriber 2 with connecting circuit No. l. The operator will also move her keys to corresponding positions so that she may converse with the subscriber to receive his instructions. 4

As soon as key 10 has been moved forward to connect subscriber 2 with connecting line I, switches 16, 26 and will be closed, causing current to flow through circuit 6. This, of course, causes operation of relay 24 to close switch 34, 50 which permits the flow of current from battery 22, I through busy lamp 40, to ground 32. Thus, busy lamp 4!) is immediately illuminated as soon as the line of subscriber 2 is connected to a connecting circuit. Thereafter busy lamp 40 will remain on until subscriber 22 either hangs up or key I0 is moved to off position.

Current will not flow through the circuit indicated by 36, 38, 58, 54 and 55 because zero potential exists at both 38 and 56. Thus, relay 5% is not in operation, and switch 58 will remain open So that no current will flow through supervisory signal 66. By the circuits described, busy lamp fill, shown in Figs. 1 and 2, and in row 12 of Fig. 3, will be illuminated, but supervisory signal 86 for circuit No. 1 will not be lighted.

If subscriber 2 desires to be connected with subscriber t and so advises the operator, the operator in turn will move key 76, shown in Fig. 3 in column '54-, (in which column all switches are connected with line 8 leading tosubscriber 4,) to upward position, thereby connecting subscriber 2 with subscriber i through connecting circuit l of the switchboard.

The line lamps which light to signal the operator initially and which go out when the operator has responded to the subscriber are shown in Fig. 3 but constitute no part of this invention, as this is common construction.

Movement of key '56 to the upward position closes switches '58, Bil and 82 of subscriber is circuit 3, which circuit is similar to the circuit already described and has therein the relay 86 from which goes wire 83 to switch 80, and thence through wire 99 to retard coil M), to the negative terminal of battery 22. The other wire from line 8 of subscriber i passes through ringing key Hi to wire 92, through switch F3 to wire 94, to the retard coil 2c, and thence to the positive terminal of the battery 22.

After key it has been moved to upward position, but before subscriber ls line has been closed by subscriber i answering the operators signal, a circuit will be completed from the positive side of the battery through wire I02, busy lamp H10, resistance t ll, switch 82, wire 58, junction 52, relay 54, and ground 55, which in turn will cause switch 63 to be closed, thereby putting the supervisory signal in operation.

With current flowing through subscriber 4s circuit, which will occur after subscriber 4 has lifted his receiver and key 16 has been moved upwardly, relay 85 will operate to close switch 96 of the supervisory circuit, thereby creating a path from the ground at 98 to junction 99 through a second busy lamp N38, to wire B2, to the positive terminal of battery 22. Lamp 1013 will then be lighted in the same manner as lamp 19 after the necessary connections have been made by the operator and subscriber 4. Another path from junction extends to resistance liii, similar to resistance 3G, through switch82 to wire 58, hereinbeiore referred to, and to junction 52.

Thus the two keys lb and 15 will be moved in the same direction, the two busy lamps Ml and Hill will be lighted, but the supervisory signal 66 of the switchboard connecting circuit 1 will be out. This condition continues until either or both of the subscribers 2 and 4 break one or both of the circuits by hanging up. Assume, for example, that the subscribers are about to hang up at the completion of the conversation.

When subscriber 2 hangs up, current will cease flowing through relay 2%, which will cause switch 3d to open, thereby breaking the circuit from the battery through busy lamp 40 to the ground, so that, were it not for the circuit through 66, 48, 58, 5 and 55, the lamp Q53 would go out completely. However, with switch 341 now open, the current from the positive terminal of battery 22,

which current formerly flowed to the ground at 32, now must pass through resistance 46, wire 58, switch 58, and relay 5 to ground 56. This current is sufiicient to bring relay 5 2 into operation so that switch 68 is immediately closed. There then becomes available a circuit from the positive terminal of battery 22 through junction dd, wires 6i! and 54, supervisory signal lamp 66, switch 68, to ground 56, so that the supervisory signal $6 is illuminated. Resistance '36 so reduces the current that busy lamp 49 is practically extinguished.

It will be seen that after switch 36 is opened by subscriber 2 hanging up, current may fiow from the positive terminal of the battery to the grounds 55 and 98. There are two paths to ground 98, one through the busy lamp will and the other through resistances it and till. There are two paths to ground 53 (assuming switch 68 not closed as yet) one which includes resistance 46 and relay 54, and the other resistance If and relay 54.

Because the combined resistances of 4-5 and iii! are greater than the combined resistances of A6 and 5 5, sufiicient current will flow through relay 5% to operate switch G8, with the result that supervisory lamp 66 will be lighted. Conversely, if subscriber t hangs up first, resistances 36 and ibl being greater than the combined resistances of Nil and 54, the relay 55 will function to cause the current of the supervisory circuit to operate relay 5 3 to close switch 68 and light supervisory lamp 66.

The operator, on observing the board, is immediately informed by virtue of lamp 86 being lighted that one or the other or both of the subscribers have broken their circuits and that attention is needed. Since it is supervisory signal 66 that is now in'operatio-n, it is indicated that the lines that need attention are those lines connected through the switchboard by connecting circuit No. 1, and by reference to the keys of circuit No. 1 that have been moved to upward position it may be determined readily which subscribers circuit has been discontinued and the appropriate key may be drawn back to ofi position. 11" key it! is operated, thereby opening switches i6, 26 and relay 56 will be rendered inoperative, switch b5; opened, and supervisory signal 66 extinguished.

If subscriber had hung up, thereby breaking circuit 8, the same result would have been obtained; namely that busy lamp tilt] would be greatly dimmed, while supervisory signal 66 would be illuminated until extinguished by movement of key'ifi to off position.

I should point out here that for each line running from a subscriber to the switchboard there is the usual line signal, shown in Fig. 3, and one busy signal, but there is only one supervisory signal for each connecting circuit that is present in the switchboard, regardless of the number of lines that may be connected through this connectingcircuit. Thus, no matter how many lines may be connected through any selected switchboard connecting circuit, the supervisory signal will always be operative to indicate the condition of lines to the board connected through the particular switchboard circuit in use when any of the subscribers lines have been broken.

Similarly, there is a supervisory signal IM, as shown in Fig.- 3, which indicates the condition of lines connected through connecting circuit No. 2, and there is another supervisory signal I06 indicating the condition of lines connected through subscribers lines coming to the switchboard as desired, although the greater the number, the more complicated the wiring will necessarily become in order that the various connections may be made through the key switches.

In further explanation of the above I have provided in Fig. 2 a diagram of a supervisory circuit for any connecting circuit on the switchboard. This circuit is the same as that of Fig. 1,

but arranged differently to show certain aspects more clearly. In this diagram the subscribers lines and connections through the connecting circuit in question are omitted for clarity in showing the operation of the supervisory circuit.

As pointed out above, for each connecting circuit there is one supervisory circuit, and this latter circuit will function in connection with any 01' all lines that may be connected to the connecting circuit under control of this supervisory circuit.

In the diagram of Fig. 2 it is contemplated that there are three subscribers lines running to the switchboard, and each of the switches 34, 96 and H6 is under the control of a relay operable when the subscribers line is closed, such relays being indicated at 24, 86 and H8. All of the relaycontrolled switches are grounded either by a common ground or individually, as at 32, 98 and I20. From each of the switches extends a wire tobusy lamps 40, I66 and I08, from which extend connections to the positive terminal of battery 22.

From each of the switches 34, 96 and H6 I also. extends a path including a resistance, as 46,

Hill and I22, and from the resistance a wire extends to the key-controlled switches 50, 82 and I24. To these switches is connected a common wire 58 which extendsto relay 54, to the ground at 56.

Connected with the lead from the positive terminal of battery 22 is wire 64, which connects with supervisory signal 66, from which runs a connection to switch 68, which is operable under the influence of relay 54.

From this diagram it is believed clear that there may be as many busy lamps, as 40,100 and I68, as there may be subscribers lines; and each busy lamp will be under the influence of a relay, as 24, 86 and H8, in that subscribers' line.

Considering the operation of subscriber 2s line, which includes relay 24, it may be seen that when that line is closed, switch 34 will be closed,

completing a path from the positive terminal of the battery, through busy lamp 40, to ground at 32, which causes the busy lamp to light. Similarly, when switches 96 and H6 are closed by virtue of other subscribers lines being in operation, busy lamps I06 and I08 will also be illuminated. With switches 34, 96 and H6 closed, the busy lamps are unaifected by the position of the key controlled switches 56, 82 and I24, as no current'will flow through these portions of the circuit because both ends of the portions in question are at ground potential at 32 and 56. Thus with switches 34, 96 and H6 closed, no current will flow through relay 54, with the result that switch 68 will remain Open and the supervisory lamp 66 will be out.

As soon, however, as any subscriber hangs up, the relay in that subscribers line will become inoperative, opening the appropriate switch on the supervisory circuit. Thus, for example, if

relay'24 becomes inoperative, switch 34 will open so that current from the battery flowing through busy lamp 453 must now pass through resistance 46 and thence through switch 50, to relay 54, to ground 56. Resistance .46 is so great that for practical purposes the current falls to a point where lamp 49 goes out, or at least becomes very But the current that does flow is sufficient to operate relay 54 to close switch 68.

As a result of this, the instant a' subscriber hangs up, the busy signal on his line goes out and the supervisory signal 66 comes on. The operator will then move the appropriate key of the circuit to which that subscriber has been connected to off position, and in this case switch 56 would be opened by the movement of key 10. As soon as switch 50 is opened, the current to relay 54 is cut off so'that the switch 68,, opens and the supervisory signal 66 goes out.

The same procedure takes place when any other subscriber hangs up, so that the operator, is-imrnediately advised of the condition of all scribers line connected to any connecting circuit has been broken by the subscriber hanging up, and, in addition, which of the lines has been broken. It is unnecessary to wait until all lines have been broken before receiving the supervisory signal. The supervisory signal becomes evident immediately upon the breaking of the circuit ofany subscriber connected to a connecting circuit.

I claim:

1. A telephone switchboard supervisory circuit comprising a plurality of parallel circuits, each including a lamp and a switch operable by a relay in series with a line, each of said parallel circuits having a common connection, said common connection including for each circuit a resistance and a manually operated switch, said common connection being connected to the ground, said ground connection including a relay, a connection extending from a point between said ground connection relay and the ground to said parallel circuits, said last-mentioned connection having therein a switch perable by said ground connection relay and a lamp.

2. A telephone switchboard supervisory circuit comprising a plurality of parallel circuits, all of said circuits including a lamp and a relay operated switch, the said switches in all of the circuits except one being operable by relaysunder the control of lines to the switchboard, the switch of said other parallel circuit being under the control of a relay in a circuit connecting each of the other parallel circuits and the ground.

3. A telephone switchboard supervisory circuit as set forth in claim 2 in which the connection between each of the other parallel circuits having line-operated relay controlled switches and the ground includes a relay, a switch, and a resistance. v

A. A telephone circuit comprising a plurality of subscribers lines, a switchboard connecting circuit, and a Supervisory circuit, a relay in and operable by each subscribers line toactuate a corresponding switch in the supervisory circuit, a plurality of key switches for simultaneously making connections in the subscribers lines and in the supervisory circuits, busy lamps in said supervisory circuit for said switchboard connecting circuit, means for actuating the busy lamp of any subscribers line when said line is in use and the key switch of the connecting circuit relating to said line is closed, a supervisory lamp and means for actuating said supervisory lamp whenever thereafter any subscribers line is broken.

5. A telephone switchboard supervisory circuit comprising a plurality of parallel circuits, each of said parallel circuits comprising a battery, a busy lamp and a relay operated switch, each of said parallel circuits having connected thereto and extending to the other terminal of the battery a circuit comprising a resistance, a key operated switch and a relay, and another circuit parallel to said last-mentioned circuit including a lamp and a switch operable by said last-mentioned relay.

6. A telephone switchboard supervisory circuit comprising a plurality of parallel circuits, each of said parallel circuits comprising a battery, a busy lamp and a relay-operated switch, each of said parallel circuits having connected thereto and extending to the other terminal of the battery a circuit comprising a resistance, a keyoperated switch and a relay, and another circuit including a power supply, a lamp and a switch operable by said last-mentioned relay.

7. A telephone switchboard supervisory circuit comprising a plurality of parallel circuits, each including a lamp and a switch operable by a relay in series with a line, each of said parallel circuits having a common connection, said common connection including for each circuit a resistance and a manually operated switch, said common connection including a relay, and a circuit including a power supply, a lamp, and a switch operable by said relay in said ground connection.

8. A telephone circuit comprising a plurality of subscribers lines, a switchboard connecting circuit and a supervisory circuit, a relay in and operable by each subscribers line to actuate a corresponding switch in the supervisory circuit, a plurality of key switches for simultaneously making connections in the subscribers lines and in the supervisory circuit, busy lamps in said supervisory circuit for said switchboard connecting circuit, means for actuating the busy lamp of any subscribers line when said line is' in use or when the key switch of the connecting circuit relating to said line is closed, a supervisory lamp, and means for causing. the operation of said supervisory lamp whenever no current is flowing in a subscribers line which is connected to said connecting circuit.

9. A telephone switchboard supervisory circuit comprising a plurality of parallel circuits, each of said circuits including a lamp and a relay operated switch, said switches in all of the circuits being operable by relays under the control of lines to the switchboard, a circuit connecting each of said parallel circuits and the ground and comprising a relay, a switch, and a resistance, a supervisory lamp in a circuit having a power supply and a switch, said last-named switch being under the control of the relay in the circuit connecting the parallel circuits and the ground.

RICHARD P. BOYER, JR. 

